Method of producing ferrous castings with cast-in ferrous inserts

ABSTRACT

A method of producing ferrous castings with cast-in ferrous metal inserts comprising the steps of preparing the surface of the ferrous metal insert which is to be cast to receive a bondable coating, applying at least one coating of a coating composition consisting of a finely divided macroscopic refractory solid particles suspended in an aqueous liquid containing a binder to the surface of the metal insert and allowing the coating to dry to form a hard non-yieldable refractory coating. The insert is then located in a mold in a manner such that it cannot be displaced during casting and a ferrous metal is cast about the refractory coated insert. The refractory coating prevents carburization of the insert and fusion of the insert with respect to the casting.

United States Patent [1 1 Davies 1 June 10, 1975 METHOD OF PRODUCING FERROUS CASTINGS WITH CAST-IN FERROUS INSERTS [75] lnventor:

[73] Assignee: Canron Limited, Montreal, Quebec,

Canada [22] Filed: Nov. 2, 1973 [21] Appl. No.: 412,177

Barry J. Davies, Hamilton, Canada 164/112 US, 110,103,105, 80, 59, 97, 78, 86, 102, 104, 98,109, 75, 72, 332, 333, 334; 75/20 R, 20 F; 249/144, 146, 147

[56] References Cited UNITED STATES PATENTS 9,350 10/1852 Yale 164/110 1,025,817 5/1912 Luckenbach 164/100 1,172,363 2/1916 Jones 164/110 2,872,715 2/1959 Bean 164/10 3,045,301 7/1962 Webbere... 164/371 3,184,815 5/1965 Reuter 22/2165 3,396,935 8/1968 Snyder 164/72 3,428,464 2/1969 Pollard 106/3823 3,461,944 8/1969 Kuebrich 164/75',100

3,468,813 9/1969 Mindick 252/313 3,509,936 5/1970 Kearfott et a1... 164/72 3,568,723 3/1971 Sowards 164/98 2,690,004 9/1954 Crawford 164/1 1 1 3,822,736 7/1974 Andionev et a1. 164/100 R26,969 10/1970 O'Shea 164/72 FOREIGN PATENTS OR APPLlCATlONS 1,904,135 9/1969 Germany 164/411 295,798 11/1969 Australia 164/72 105,075 10/1917 United Kingdom 164/41 1 1,240,944 7/1971 United Kingdom.... 164/75 1,191,202 5/1970 United Kingdom 164/332 Primary Examiner-Francis S. Husar Assistant ExaminerV. K. Rising Attorney, Agent, or Firm-Fetherstonhaugh & Co.

[57] ABSTRACT A method of producing ferrous castings with cast-in ferrous metal inserts comprising the steps of preparing the surface of the ferrous metal insert which is to be cast to receive a bondable coating, applying at least one coating of a coating composition consisting of a finely divided macroscopic refractory solid particles suspended in an aqueous liquid containing a binder to the surface of the metal insert and allowing the coating to dry to form a hard nonyieldab1e refractory coating. The insert is then located in a mold in a manner such that it cannot be displaced during casting and a ferrous metal is cast about the refractory coated insert. The refractory coating prevents carburization of the insert and fusion of the insert with respect to the casting.

1 Claim, 4 Drawing Figures METHOD OF PRODUCING FERROUS CASTINGS WITH CAST-IN FERROUS INSERTS FIELD OF INVENTION This invention relates to the production of ferrous castings with cast-in ferrous metal inserts. In particular, this invention relates to an improved method of preventing carburization and fusion of a cast-in ferrous metal insert with respect to a ferrous casting.

PRIOR ART It has previously been proposed to cast-in a ferrous metal insert such as a steel bolt or a nodular cast iron insert or the like to prevent the necessity of forming cored openings in cast plates and the like into which bolts are subsequently fitted. It has, however, been found that as a result of casting around a bolt or the like the steel of which the bolt is made is carburized to the extent that the bolt loses its ductility and becomes brittle. For this reason, there has been only limited use of the practice of casting-in bolts or the like.

Castings have also been reinforced by means of reinforcing rod structures. The reinforcing rod structures have previously been coated in a special apparatus with a mixture of resin and sand. The reinforcing member must be preheated and thereafter placed in a special apparatus and covered with a mixture of resin and sand. The reinforcing structure must remain in the apparatus for a period of time sufficient to permit a buildup of the required thickness of the surface layer. The coating which has been applied at this stage is soft and may easily be damaged in handling. In order to harden the coating, the reinforcing member with the coating applied must again be heated to a temperature sufficient to set the coating. This is a costly and time consuming method which requires a complex apparatus. It will also be apparent that when very large reinforcing structures are to be used, the apparatus in which the coating is to be applied must also be very large. In addition, the presence ofa resin in the mixture of the coating tends to cause gases to be generated during the casting process which adversely affects the quality of the casting. Furthermore, because the coating has a substantial thickness and it includes a sand mass, it is subject to spalling" and must, therefore, be handled with care.

SUMMARY OF INVENTION The present invention overcomes the difficulties of the prior art described above and provides a simple and efficient method of producing a ferrous casting with cast-in ferrous metal inserts comprising the steps of preparing the surface of the ferrous metal insert which is to be cast-in to receive a bondable coating, applying at least one coating of a refractory coating which when set is capable of resisting carburization and fusion during casting, locating the insert in a mold in a manner such that it cannot be displaced during casting and casting a ferrous metal about the insert.

The present invention also provides an improved ferrous casting having cast-in ferrous metal inserts cornprising a body of cast ferrous material having cast-in ferrous metal inserts coated with a thin, hard, nonyieldable refractory coating capable of resisting carburization and fusion during the casting operation, said coating having an outer surface which is slidable with respect to said casting to permit relative movement of the casting with respect to the inserts.

PREFERRED EMBODIMENT The invention will be more clearly understood after reference to the following detailed specification read in conjunction with the drawings wherein FIG. 1 is a partially sectioned pictorial view illustrating a casting with a cast in ferrous metal insert in the form of a threaded bolt;

FIG. 2 is a partially sectioned pictorial view of a casting with a ferrous metal shaft cast therein;

FIG. 3 is a partially sectioned pictorial view illustrating a cast'in ferrous metal reinforcement; and

FIG. 4 is a view similar to FIG. 3 showing an alternative form of cast-in ferrous metal reinforcement.

With reference to FIG. I of the drawings, it will be seen that the bolt 10 may be conveniently positioned with respect to a casting 12 by casting around the head of the bolt. This is achieved by applying a coating of the type which will be described hereinafter to the surface of the bolt 10 and thereafter locating the bolt 10 in the mold and thereafter casting the ferrous metal about the bolt head to provide the combination of a casting and bolt as illustrated in FIG. 1. The bolt is preferably made from a strong ductile steel material while the casting may be made from steel or cast iron. One of the difficulties which has previously been experienced with respect to the location of cast-in steel inserts such as bolts has been that the bolt is carburized by reason of the fact that it comes in intimate contact with the cast metal, with the result that the bolt loses its ductility and is brittle. This is particularly undesirable in a cast-in structure because of the difficulty of replacing a bolt which has been broken or damaged in use. Carburization is a particularly serious problem due to the high carbon content of most cast irons such as white, grey and nodular cast irons.

In FIG. 2 of the drawings the insert is in the form of a shaft I4 which may be made from a nodular cast iron or steel or the like, about which a cylindrical shaped casting 16 is formed. Again, the surface of the shaft 14 is coated with the refractory coating as will be described hereinafter and located in a position within the mold such that it cannot be displaced during casting. The cylindrical casting is then formed about the shaft 14.

A feature of the inserts l0 and 14 of the embodiments illustrated in FIGS. 1 and 2 of the drawings is that they are exposed at one or more surfaces of the casting. This permits the insert to function as a component used to operably connect or unite the cast member to complementary component parts of an assembly in which the cast element is to be used.

According to a further embodiment of the present invention, the cast-in insert may be in the form of a reinforcing element such as the expanded sheet metal element 18 of FIG. 3. The expanded sheet metal element I8 is located within the body of a casting 20. Again, the expanded metal reinforcement 18 is coated with the refractory coating of the type described hereinafter prior to the formation of a casting. In the event of a cracking or failure of the material of the casting, the reinforcing element 18 serves to hold the casting together. Because of the fact that carburization is prevented, the reinforcing structure retains its inherent ductility so that it will not fracture simultaneously with the structure of the casting. Because the coating prevents fusion between the reinforcing and the casting. the reinforcement is not excessively strained by expansion or contraction of the casting.

A still further embodiment of the invention is illustrated in FIG. 4 of the drawings wherein the casting 22 is reinforced by a welded frame structure 24 which consists of a plurality of rods 26 and 28 which are secured to one another as by welding into a grid pattern. After formation of the grid pattern, the reinforcement is coated with a coating to be described hereinafter and the casting formed around the reinforcement in a mold.

It has been found that a coating composition suitable for application to a ferrous metal insert, such as steel or nodular cast iron which is to be cast-in a ferrous casting, consists of a macroscopic finely divided refractory solid particles suspended in a aqueous liquid containing a binder. A suitable composition may be a vitreous silica dispersion. Alternative compositions may include non-silicose refractories such as alumina and graphite. The binder is preferably in the form of a colloidal silica so]. The proportions of the refractory solid particles and the aqueous liquid containing the binder are preferably within the range of to 70% by weight and 30 to 90% by weight respectively. The suspension is stabilized by intimate dispersion therewith and the stabilizing amount of xanthomonas hydrophylic colloid. A coating of this type which has been found to have satisfactory resistance to carburizing is presently used to prevent fusion of cast ingots to an ingot stool. The problems associated with carburization are critical to the present invention but are not of any concern in the use of the coating in association with an ingot cast ing stool. The only problem encountered in this application is one of fusion.

A coating suitable for use in the present invention is known by the registered trade mark NALCOTE 4l20 and is manufactured by Alchem Limited of Burlington, Ontario. It has been found that a coating thickness of the order of about 0.005 inches provides adequate protection in most casting, however, the thickness can be increased if necessary by the application of additional coats to 0.015 inches or more as required.

According to the method of the present invention, the ferrous metal insert or reinforcement is shaped or formed if necessary to the required configuration. This may require bending and/or welding of the steel components as previously described. When the structure is welded, it is sometimes desirable to stressrelieve the structure to relieve the stresses caused by welding. The steel insert is cleaned to remove all dirt, rust, mill scale, grease, oil or the like so that the surface of the insert is bondable with the coating which is subsequently applied. lf the surface of the insert is smooth and polished, it is desirable to shot blast the surface to provide a surface finish which is conducive to good adhesion with the coating. While it is not essential to the formation of the layer of the coating, the insert may be preheated prior to the application of the coating to approximately l50F. in order to hasten the drying of the coating. The insert is then coated with Le coming composition previously described. The coating may be applied with a brush, by spray ng or by dipping or the like. It has been found that a single coating of the composition previously described is generally sufficient. However, additional coatings may be applied if desired. The coating is then allowed to dry. Drying of the coating may be assisted by blowing warm air or by the application of heat lamps or the like. If this post-dry mg operation is carried out, the preheating step previoiusly described may be eliminated. When the coating has dried, it forms a thin, hard, non-yieldable refractory coating on the surface of the steel insert. The steel insert is then previously in a mold in such a manner that it will not move during the casting operation except as a result of minor warpage which may occur during casting. The molten ferrous metal which may be in the form of white, grey or nodular cast iron, or any combination thereof, or cast steel, is then cast into the mold in such a manner that the ferrous metal insert is embedded in the casting.

From the foregoing it will be apparent that the present invention provides a simple and efficient method of forming a ferrous casting with a cast-in ferrous metal insert. This method permits the coating to be applied without difficulty and is not restricted by the dimensional characteristics of the apparatus in which coating is carried out. These and other modifications will be apparent to those skilled in the art without departing from the scope of the invention.

What I claim as my invention is:

l. A method of producing ferrous castings with castin ferrous metal inserts comprising the steps of a. preparing the surface of the ferrous metal insert which is to be cast-in to receive a bondhle coating,

b. applying at least one coat of a coating composition consisting of finely divided macroscopic vitreous silica dispersed in an aqueous silica sol containing a binder to the surface of the ferrous metal insert and allowing the coating to dry to form a hard nonyieldable refractory coating which prevents carburization and fusion during the casting step,

c. locating the coated insert in a mold in a manner such that it cannot be displaced during casting,

d. casting a ferrous metal about said refractory coated insert, said refractory coating preventing carburization of the insert and fusion of the insert with respect to the casting. 

1. A METHOD OF PRODUCING FERROUS CASTINGS WITH CAST-IN FERROUS METAL INSERTS COMPRISING THE STEPS OF A. PREPARING THE SURFACE OF THE FERROUS METAL INSERT WHICH IS TO BE CAST-IN TO RECEIVE A BONDABLE COATING, B. APPLYING AT LEAST ONE COAT OF A COATING COMPOSITION CONSISTING OF FINELY DIVIDED MACROSCOPIC VITREOUS SILICA DISPERSED IN AN AQUEOUS SILICA SOL CONTAINING A BINDER TO THE SURFACE OF THE FERROUS METAL INSERT AND ALLOWING THE COATING TO DRY TO FORM A HARD NONYIELDABLE REFRACTORY COATING WHICH PREVENTS CARBURIZATION AND FUSION DURING THE CASTING STEP, C. LOCATING THE COATED INSERT IN A MOLD IN A MANNER SUCH THAT IT CANNOT BE DISPLACED DURING CASTING, D. CASTING A FERROUS METAL ABOUT SAID REFRACTORY COATED INSERT, SAID REFRACTORY COATING PREVENTING CARBURIZATION OF THE INSERT AND FUSION OF THE INSERT WITH RESPECT TO THE CASTING. 